Cardiovascular disease (CVD) is the foremost killer of women in the U.S. Two thirds of sudden cardiac deaths in women have no clinical warning signs, and therefore can only be avoided by early prevention. Obesity is a well established contributor to CVD in women and men. Longitudinal studies indicate young adults who gain weight substantially increase lifetime risk of CVD. Weight gain raises risk even in individuals who already developed overweight status in childhood. The National Institutes of Health and particularly the National Heart, Lung and Blood Institute have identified a need for sustainable, cost effective interventions to prevent weight gain in young adults. To meet this need we propose a peer education intervention to improve diet and physical activity behaviors in female university freshmen. Three hundred freshmen will be randomized to an 8 week course in weight management directed by female peers of similar racial/ethnic background or to a control group. Peers will be selected from upper-level students in Nutritional or Exercise Sciences and related disciplines, and will be selected and trained for communication and interpersonal skills during the semester preceding the course. The peer delivered intervention will disseminate evidence-based national guidelines for a healthy diet, regular physical activity and weight management, as well as provide social modelling of healthy behaviors by peers, opportunities to practice healthy behaviors and positive reinforcement for successful implementation of these behaviors in the participants' lives. The intervention is designed to increase participants' knowledge and self-efficacy for meeting national weight, diet and exercise guidelines. Changes in participants' weight, waist circumference, diet and activity records and self-efficacy for healthy behavior will be compared at the end of the freshman year and at the end of their sophomore and junior years (2 year follow-up). A subsample of participants (n=150) will also be assessed for key CVD risk factors: dyslipidemia, hypertension, and insulin resistance. We anticipate the peer education intervention will improve diet and physical activity behaviors and reduce weight gain and development of CVD risk. If successful, this peer education program can be applied in other university settings as a sustainable and cost effective approach to reducing the burden of obesity and CVD.